Dear ALL,
I am getting the different no. of allowable design of cycles for Fatigue using the clause of ASME section VIII div.2 Part5, 3F.1.2 .3F.1.2 says that you can calcuate the allowable design cycles using the equation 3.F.1 or Table 3.F.10.
Sa = 12000 psi, Material table 3.F.4, Et / Efc = 22800000 / 28300000
1. (Euation 3.F.1) If we put the values in equation (with all C constants, X =2.41, Sa=12 ksi ) then we get N = 205 cycles.
2. (Table 3.F.10) If use the table, for Sa=12 ksi then N= more than 1000000 cycles

How the different cycles coming by using the same clause
It will be great if anybody help to me.

Prashant

Hello Prashant,
are you sure that your X=2,4 is correct? Depending on the curve of the material I get 9,2; 4,9 or 6,6, which results in a significant higher number of cycles.

I have just compared the tabulated values of 3.F.10 with 3.F.4 and some other tables and the numbers of cycles are pretty close together.

Michael

Dear Prashant,
I have checked for 12 ksi. X is around 6.3097. Please use appropriate ci constants as sa is less than 31 ksi. Hence the number what you got Table 3.f.10 is correct and you will get closer to same from Table 3.f.1 as X is nearly 6.3097

_________________
R.SRINIVASAN
Sr. VICE PRESIDENT
Head, Design and Engineering
PED,ISGEC,
YAMUNANAGAR
HARYANA -135001
INDIA